body{
    background-image: url("https://img0.baidu.com/it/u=3072953094,4063084816&fm=26&fmt=auto&gp=0.jpg");
    background-repeat: no-repeat;
    background-size: 100%;
    /*color: white;*/
}
#vm_div{
    position: relative;
    top: 2em;
    margin: 0 auto;
    background-color: rgba(100,200,200,0.5);
    width: 30em;
    height: 30em;
    box-shadow: 5px 10px 20px gray;
}
#vm_div table{
    position: relative;
    top: 5em;
    margin: 0 auto;
    width: 20em;
    height: 20em;

}
#vm_div table input{
    width: 25em;
    height: 3em;
}